TRIPOLI - Abdullah al-Senussi, Libya's feared former intelligence chief, was cornered and captured at a remote desert homestead on Sunday, a day after Muammar Gaddafi's son was seized by Libyan fighters in the same region.The arrest of the last survivor of the old regime who is wanted at The Hague for crimes against humanity crowned a momentous couple of days for a new government that is still in the process of formation, and also posed immediate tests of its authority -- both over powerful militias and with world powers.RELATED:Gaddafi's son captured, scared and without fightEU urges Libya to work with ICC over captured Gaddafi sonIn a sign of the strain that the prime minister-designate is under to reconcile the interests of rival militia groups that control the ground in Libya, officials said Abdurrahim El-Keib had asked for another couple of days to complete a cabinet that he had previously hoped to announce on Sunday.A commander of former rebel forces nominally loyal to the National Transitional Council (NTC), General Ahmed al-Hamdouni, told Reuters that his men, acting on a tip, had found and surrounded Senussi at a house belonging to his sister near the town of Birak, about 500 km (300 miles) south of Tripoli and in the same general area as Saif al-Islam was seized on Saturday.NTC spokesman Abdul Hafez Ghoga later confirmed that Senussi, who is Saif al-Islam's uncle by marriage, had been captured. It was not immediately clear if the arrests were linked, though there has been speculation since the fall of Tripoli three months ago that the pair were hiding together.Fighters who intercepted Saif al-Islam on a desert road in the early hours of Saturday said they believed one of his companions was also a nephew of Senussi, whose wife is a sister of Muammar Gaddafi's second wife Safiya.Like Muammar Gaddafi, who was captured and killed on the coast a month ago on Sunday, Saif al-Islam and Senussi were indicted this year by the International Criminal Court for alleged plans to kill protesters after the Arab Spring revolt erupted in February. But NTC officials have said they can convince the ICC to let them try both men in Libya.Ghoga said NTC members meeting on Sunday had confirmed that preference, as did the current justice minister -- although legal experts point out that international law demands Tripoli make a strong case for the right to try anyone who has already been indicted by the ICC.Many Libyans want Gaddafi son, intel chief hangedGiven the state of Libya's legal system after 42 years of dictatorship, as well as the depth of feelings after this year's civil war, the ICC may not agree. Its chief prosecutor is expected in Libya this week.While the ICC, backed by a UN resolution, can demand Libya hand over the prisoners, many Libyans are keen to see them tried for alleged crimes committed over decades, well beyond the scope of the ICC charges relating to this year only. And many also want them hanged, something barred at The Hague.Among other old wounds, Senussi is suspected of a key role in the killing of more than 1,200 inmates at Tripoli's Abu Salim prison in 1996. It was the arrest of a lawyer for victims' relatives that sparked Libya's Arab Spring revolt in February. And many of the dead were members of Islamist groups which are expected to be a major political force in a democratic Libya.The case of Senussi, long the elder Gaddafi's right-hand man and enforcer, may also revive interest in international incidents long shrouded in mystery, from the days in the 1980s and 90s when Gaddafi's Libya waged undercover war on the West. Senussi's name has been linked with the Lockerbie bombing of 1988. He was among six Libyans convicted in absentia in Paris of bringing down a French UTA airliner a year later.